Loans and Allowance for Loan Losses - Troubled Debt Restructurings, Excluding Loans Acquired, Segregated by Class of Loans (Details) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019 USD ($) loan	Sep. 30, 2018 loan	Sep. 30, 2019 USD ($) loan	Sep. 30, 2018 loan	Dec. 31, 2018 USD ($) loan
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts	1	6	1	8
Loans, Excluding Acquired Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts			28		33
Troubled debt, balance | $	$ 8,277		$ 8,277		$ 9,215
Loans, Excluding Acquired Loans | Accruing TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts			12		12
Troubled debt, balance | $	6,519		$ 6,519		$ 6,369
Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts			16		21
Troubled debt, balance | $	$ 1,758		$ 1,758		$ 2,846
Real Estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts	1	3	1	4
Real Estate | Loans, Excluding Acquired Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts			21		23
Troubled debt, balance | $	$ 5,389		$ 5,389		$ 5,664
Real Estate | Loans, Excluding Acquired Loans | Accruing TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts			8		8
Troubled debt, balance | $	3,715		$ 3,715		$ 3,536
Real Estate | Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts			13		15
Troubled debt, balance | $	1,674		$ 1,674		$ 2,128
Real Estate | Construction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts		1		1
Real Estate | Construction | Loans, Excluding Acquired Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts			1		3
Troubled debt, balance | $	97		$ 97		$ 485
Real Estate | Construction | Loans, Excluding Acquired Loans | Accruing TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts			0		0
Troubled debt, balance | $	0		$ 0		$ 0
Real Estate | Construction | Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts			1		3
Troubled debt, balance | $	$ 97		$ 97		$ 485
Real Estate | Single family residential
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts	1		1	1
Real Estate | Single family residential | Loans, Excluding Acquired Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts			16		16
Troubled debt, balance | $	$ 1,176		$ 1,176		$ 846
Real Estate | Single family residential | Loans, Excluding Acquired Loans | Accruing TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts			6		6
Troubled debt, balance | $	549		$ 549		$ 230
Real Estate | Single family residential | Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts			10		10
Troubled debt, balance | $	627		$ 627		$ 616
Real Estate | Other commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts		2		2
Real Estate | Other commercial | Loans, Excluding Acquired Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts			4		4
Troubled debt, balance | $	4,116		$ 4,116		$ 4,333
Real Estate | Other commercial | Loans, Excluding Acquired Loans | Accruing TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts			2		2
Troubled debt, balance | $	3,166		$ 3,166		$ 3,306
Real Estate | Other commercial | Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts			2		2
Troubled debt, balance | $	950		$ 950		$ 1,027
Commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts		3		3
Commercial | Loans, Excluding Acquired Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts			7		10
Troubled debt, balance | $	2,888		$ 2,888		$ 3,551
Commercial | Loans, Excluding Acquired Loans | Accruing TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts			4		4
Troubled debt, balance | $	2,804		$ 2,804		$ 2,833
Commercial | Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts			3		6
Troubled debt, balance | $	84		$ 84		$ 718
Commercial | Commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts		3		3
Commercial | Commercial | Loans, Excluding Acquired Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts			7		10
Troubled debt, balance | $	2,888		$ 2,888		$ 3,551
Commercial | Commercial | Loans, Excluding Acquired Loans | Accruing TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts			4		4
Troubled debt, balance | $	2,804		$ 2,804		$ 2,833
Commercial | Commercial | Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts			3		6
Troubled debt, balance | $	$ 84		$ 84		$ 718